1. Technical Field
The present invention relates to a positioning system for carrying out positioning based on signals from positioning satellites; a terminal apparatus, a terminal apparatus control method; a terminal apparatus control program; and a computer readable recording medium having the terminal apparatus control program recorded therein.
2. Related Art
In the past, there has been a practically available positioning system for positioning a current position of a GPS receiver by utilizing, for example, a GPS (Global Positioning System) that is a satellite navigation system (JPA-2000-131415 (FIG. 1 or the like), for example).
The GPS receiver, for example, computes an observable GPS satellite positioned above in the sky, and, for example, selects a group of four GPS satellites. Then, the GPS receiver receives signals(hereinafter, referred to as satellite signals) from each GPS satellite with respect to each group of GPS satellites, and obtains a distance (hereinafter, referred to as a pseudo distance) between each GPS satellite and the GPS receiver by a difference(hereinafter, referred to as a delay time) between a time at which a satellite signal was transmitted from each GPS satellite and a time at which the satellite signal arrived at the GPS receiver. The GPS receiver is designed to compute a positioning result of a current position by using a position of each GPS satellite on a satellite orbit and the above described pseudo distance. The GPS receiver is design to compute a positioning result of each group of GPS satellites and to select and output a position determined to be close to a true position from among a plurality of positioning results.
In the meantime, a GPS satellite passes on its satellite orbit, and thus, a receiving direction and a pseudo distance of a satellite signal fluctuates regardless of whether the GPS receiver passes or stops. Thus, the GPS receiver may output a position in a direction different from an actual passing direction of the GPS receiver depending on a receiving state of a satellite signal or may output a position different from a previously output position regardless of the fact the GPS receiver has stopped ever since it has been previously positioned. In this case, there is a problem that an output position deviates from a true position, and precision deteriorates.